This invention relates to internal combustion engines, and in particular, to an improved throttle structure for controlling fuel input to the combustion chambers of the engine, and for mixing and modulating liquid fuel and intake air in order to reduce undesirable exhaust emissions from such engines.
In combustion engines prevalent today, the combustion chambers of the engine are connected to a source of fuel and a source of air through an intake manifold and a carburetor. The carburetor has a main air passageway extending through it, and a venturi restriction is used to draw fuel into the air stream. Control of the flow through the air passageway is obtained through the use of a throttle valve. The throttle valve conventionally has been a butterfly valve type of device.
It long has been known that the combustion chambers of an engine receive varying amounts of fuel during operation of the engine. Ideally, each intake stroke of the piston would draw a fuel/air mixture into a particular combustion chamber which would burn completely during the power stroke of the piston. Unfortunately, fuel distribution does not match the ideal. The reasons for unequal distribution also generally are known. Thus, when the fuel/air mixture strikes a conventional throttle valve, large droplets of fuel often are formed. Large fuel droplets do not move readily to the combustion chambers, and distort the fuel/air ratio when they do arrive. In addition, the throttle valve commonly is pivotally mounted across the diameter of the carburetor air passageway. Fluid movement past the throttle is unbalanced or directed toward one side or the other of the passageway by the very presence of the throttle valve. Although some mixing of the two air streams imposed by the throttle valve does occur below the throttle valve, the asymmetrical distribution of the fuel and the intake air rarely is overcome completely.
A number of attempts have been made to improve the consistency of the air/fuel mixture delivered to the cylinders in an internal combustion engine. In general, prior art attempts involve complicated redesigns of the fuel/air delivery system, for example, by the use of fuel injection mechanisms, or complicated redesigns of the engine. While such systems and designs work for their intended purposes, they are expensive to produce initially, and often are expensive to maintain in normal operation and use.
An example of an improved throttle structure with which the invention disclosed hereinafter is compatible is disclosed in a co-pending application by James T. Bickhaus, "Throttle Structure for an Internal Combustion Engine," Ser. No. 727,713, filed 9/29/76. An invention dealing with subject matter related to that described herein is disclosed in a co-pending application by Donald L. Hicks, "Throttle Structure for Imparting Supersonic Flow Characteristics in the Intake Manifold of an Internal Combustion Engine," Ser. No. 727,718, filed 9/29/76. Both applications are assigned to the assignee of the present invention. General information disclosed in these co-pending applications is intended to be incorporated by reference.
The invention disclosed hereinafter provides an improved throttle means for a conventional carburetor, which accomplishes supersonic flow with simplified structure. As described more fully hereinafter, the incoming fuel and air mixture, in one embodiment of the invention, is permitted to strike the bottom wall of the intake manifold of the engine. A throttle means, which may be similar to that described in the above-referenced Bickhaus application, Ser. No. 727,713, filed 9/29/76, in conjunction with the bottom wall, is utilized to regulate fluid flow in accordance with engine demand. The throttle means and intake manifold are arranged so that fluid flow through the throttle passes through a restriction for obtaining sonic flow, and a diverging portion which imparts supersonic and then subsonic flow to the mixture.
Devices and methods for obtaining supersonic flow in the fuel supply system of internal combustion engines also are known in the art. For example, the U.S. Pat. No. 3,778,0388 to Eversole, issued Dec. 11, 1973, describes a particular approach to obtaining such supersonic flow.
In distinction to prior art designs, this invention accomplishes supersonic flow with little modification either to the conventional carburetor structure or to the conventional intake manifold.
One of the objects of this invention is to provide a throttle structure for an internal combustion engine which gives a better fuel/air mixture distribution to the cylinders of the engine.
Another object of this invention is to provide a throttle valve structure having an inlet side and an outlet side, the outlet side being positioned in the inlet manifold of an internal combustion engine.
Another object of this invention is to provide a throttle valve structure which utilizes a tubular body member as the valve element.
Yet another object of this invention is to provide a throttle valve structure which imparts supersonic flow to the fuel mixture passing through it.
Yet another object of this invention is to provide a throttle structure imparting supersonic flow characteristics to the fluid mixture passing through it, without requiring major design changes in either the carburetor or the intake manifold of the engine.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.